Anti-yellowing polycondensation polymer compositions and articles

ABSTRACT

A composition, having an improved resistance to yellowing under heat aging, comprising at least 20 weight % of at least one polycondensation polymer having a heat deflection temperature of above 80° C. under a load of 1.82 MPa when measured according to ASTM D648, from 0 to 5 weight % of at least one polymer having a heat deflection temperature of at most 80° C. under a load of 1.82 MPa when measured according to ASTM D648, a white pigment; and a black pigment provides resistance to heat aging induced yellowing. The polycondensation polymers are advantageously selected from the group consisting of polyarylethersulfones, at least partially aromatic polyamides, polyamideimides, liquid crystalline polymers, polyimides, polyetherimides, polyaryletherketones, and polyphenylene sulfides. The polymer composition can be molded to form a variety of articles, including LED components, such as reflectors, reflector cups, and scramblers.

CROSS REFERENCE TO PROVISIONAL APPLICATIONS

This application is a Continuation application of U.S. application Ser.No. 10/531,251, filed Oct. 7, 2005, now allowed, which is a 371application of PCT/US03/32603, filed Oct. 15, 2003, and claims benefitof U.S. provisional application Ser. No. 60/418,184, filed Oct. 15,2002, the entire disclosures of all of which are incorporated herein byreference.

TECHNICAL FIELD

This invention is directed to polycondensation polymer compositionshaving an improved resistance to yellowing under heat aging, andarticles formed from the polymer compositions, including reflectors,reflector cups, and scramblers for light emitting diodes.

BACKGROUND OF THE INVENTION

Light emitting diode (LED) components, such as reflectors, reflectorcups, and scramblers are typically formed from polymer compositions. LEDapplications require polymer compositions with good opacity andreflective properties. Various useful polymer compositions for LEDapplications are known, these ones usually include polycondensationpolymers, such as polyphthalamides. One problem noted with the prior artcompositions used in LED applications is yellowing upon heat aging.

LED components are exposed to elevated temperatures during themanufacturing process. For example, during the fabricating steps the LEDcomponents are heated to about 180° C. to cure an epoxy pottingcompound. The LED components are also exposed to temperatures above 260°C. while soldering operations are performed. In addition, while in use,LED components, such as automobile components, are routinely subjectedto temperatures above 80° C. This exposure to high temperatures causesyellowing of polymer compositions used for forming LED components.

Another polymer composition used for LED components comprisespolycarbonate. Polycarbonate compositions, however, soften when exposedto the epoxy curing and soldering temperatures. LED components formedfrom polycarbonate compositions would not retain their shape at thesetemperatures.

Yellowing is a particularly acute problem for blue light LEDs. Yellowsurfaces absorb blue light. Thus, yellow reflectors absorb blue lightrather and are, therefore, inefficient reflectors.

SUMMARY OF THE INVENTION

There exists a need in the reflector art for polycondensation polymercompositions capable of withstanding long-term exposure to hightemperatures. There exists a need in the reflector art forpolycondensation polymer compositions that do not yellow upon heataging. There exists a need in the reflector art for reflectors,reflector cups, and scramblers formed from polycondensation polymercompositions that resist yellowing upon heat aging while maintainingexcellent opacity and reflective properties.

These and other needs are met by certain embodiments of the presentinvention that provide a polymer composition comprising at least 20weight % of at least one polycondensation polymer having a heatdeflection temperature of above 80° C. under a load of 1.82 MPa whenmeasured according to ASTM D648. The composition further comprises from0 to 5 weight % of at least one polymer having a heat deflectiontemperature of at most 80° C. under a load of 1.82 MPa when measuredaccording to ASTM D648. In addition, the polymer composition comprises awhite pigment and a black pigment.

In certain embodiments of the present invention, the polycondensationpolymer is selected from the group consisting of polyarylethersulfones,at least partially aromatic polyamides, polyamideimides, liquidcrystalline polymers, polyimides, polyetherimides, polyaryletherketones,and polyphenylene sulfides.

These and other needs are further met by certain embodiments of thepresent invention that provide a shaped article formed from the polymercomposition as above detailed.

These and other needs are additionally met by certain embodiments of thepresent invention wherein the shaped articles are a reflector for anLCD, reflector cup for a surface mount LED, or a scrambler for aseven-segment light LED.

In addition, these and other needs are met by a method of forming ashaped article comprising providing a polymer composition as abovedetailed.

Furthermore, these and other needs are met by using a black pigment toimprove the heat-stability of a white-pigmented polycondensation polymercomposition.

In certain embodiments of the present invention, the black pigment is acarbon black, the white pigment is titanium dioxide, and thepolycondensation polymer is a polyphthalamide.

The present invention provides a new polymer composition that inhibitsyellowing of high-temperature polycondensation polymers upon heat aging.The present invention provides reflectors, reflector cups, andscramblers with excellent opacity and reflective properties.

The present invention also provides a cost effective polycondensationpolymer composition for use in reflectors, reflector cups, andscramblers. The present invention addresses the longstanding limitationof yellowing of polycondensation polymers upon heat aging.

Additional advantages and aspects of the present invention will becomereadily apparent to those skilled in the art from the following detaileddescription, wherein embodiments of the present invention are shown anddescribed, by way of illustration of the best mode contemplated forpracticing the present invention. As will be described, the presentinvention is capable of other and different embodiments, and its severaldetails are susceptible to modification in various obvious respects, allwithout departing from the spirit of the present invention. Accordingly,the description is to be regarded as illustrative in nature, and not aslimitative.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a LED reflector cup according to anembodiment of the instant invention.

FIG. 2 illustrates a seven segment scrambler for an LED according to anembodiment of the instant invention.

FIG. 3 is a plot of reflectivity versus wavelength for polycondensationpolymer compositions according to embodiments of the present invention.

FIG. 4 is a plot of heat aged reflectivity versus wavelength of lightfor polycondensation polymer compositions according to embodiments ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

In many applications polymers that are capable of withstanding elevatedtemperatures, and that have good strength, and tolerance to a host ofchemical environments are required.

Polymers that are suitable for use in the present invention arepolycondensation engineering polymers. Polycondensation polymers arepolymers that are formed from a repeating condensation reaction.Engineering polymers are thermoplastics that advantageously maintaindimensional stability and most mechanical properties above 80° C. andbelow 0° C. Engineering polymers can be advantageously formed intofunctional parts that can bear loads and withstand abuse in temperatureenvironments commonly experienced by traditional engineering materials,such as wood, metals, glass, and ceramics.

Aromatic polycondensation polymers, in particular, provide hightemperature service, high strength, and chemical resistance. Aromaticpolycondensation polymers are polymers formed by the condensationreaction of two compounds, wherein at least one of the compoundscomprises at least one aromatic group. Aromatic polycondensationpolymers are well suited for forming LED components.

Polycondensation polymers that are suitable for certain embodiments ofthe present invention are high temperature polycondensation polymers.High temperature polycondensation polymers are defined aspolycondensation polymers that have a heat deflection temperature (HDT)of above 80° C. under a load of 1.82 MPa when measured according to ASTMD648. Typical heat deflection temperatures of certain polycondensationpolymers are listed in Table 1.

TABLE 1 High Temperature Polycondensation Polymers Heat DeflectionPolycondensation Polymer Temp. (° C.) Polysulfone 174 Polyethersulfone203 Polyphenylsulfone 204 Polyphthalamide 120 Polyamideimide 278 Liquidcrystalline polymers (LCP) 180-310 (there are several differentconventional LCPs) Polyimide 360 Polyetherimide 200 Polyetheretherketone(low flow) 160 Polyetheretherketone (high flow) 171 Polyphenylenesulfide 135 Polycarbonate 132

Heat deflection temperatures of polymers and polymer compositions aredetermined according to ASTM D648, Method A, using a span of 4 inches.The polymer is injection molded into plaques that are 5 inches long, ½inch wide, and ⅛ inch thick. The plaques are immersed in a suitableliquid heat-transfer medium, such as an oil, during the HDT test. DowCorning 710 silicone oil, for example, is used for polyphthalamidepolymers and compositions. For polycondensation polymers andcompositions, such as polyphthalamides and polyphthalamide compositions,the HDT test is performed on unannealed specimens.

In the present invention, the addition of a black pigment to apolycondensation polymer composition unexpectedly provides resistance toheat aging induced yellowing of articles formed from the composition,such as LED components. Polymer compositions according to the presentinvention comprise a polycondensation polymer, a white pigment, and ablack pigment.

In certain embodiments of the present invention, the polycondensationpolymer is present in the polymer composition in a concentration of atleast about 55 weight %. In certain other embodiments of the presentinvention, the polycondensation polymer is present in the polymercomposition in a concentration of at least about 43 weight %. In certainother embodiments of the present invention, the polycondensation polymeris present in the polymer composition in a concentration of at leastabout 40 weight %. In certain embodiments of the present invention, thepolycondensation polymer is present in the polymer composition in aconcentration of up to about 90 weight %. In certain other embodimentsof the present invention, the polycondensation polymer is present in thepolymer composition in a concentration of up to about 75 weight %. Theconcentration of polymer in the polymer composition is based on thetotal weight of the polymer composition.

Suitable polycondensation engineering polymers for use in certainembodiments of the present invention include polyarylethersulfones, atleast partially aromatic polyamides, polyamideimides, liquid crystallinepolymers, polyimides, polyetherimides, polyaryletherketones, andpolyphenylene sulfides.

In certain embodiments of the present invention, suitable at leastpartially aromatic polyamides are polyphthalamides. Suitablepolyphthalamides for certain embodiments of the present invention areformed by a polycondensation reaction between at least one aromaticdicarboxylic acid and a diamine. In certain embodiments, the aromaticdicarboxylic acid is terephthalic acid. In certain other embodiments ofthe present invention, the polyphthalamide further comprises isophthalicacid residues. In other certain embodiments of the present invention,the polyphthalamide is further formed from an aliphatic dicarboxylicacid, such as adipic acid. In certain other embodiments of the presentinvention, the diamine is an aliphatic diamine. Suitable aliphaticdiamines for certain embodiments of the present invention comprise 4 to12 carbon atoms, such as hexamethylene diamine (HMDA), nonane diamine,2-methyl-1,5 pentadiamine, and 1,4-diaminobutane. Suitablepolyphthalamides for certain embodiments of the present invention aredisclosed in U.S. Pat. Nos. 5,436,294; 5,447,980; and Re34,447; theentire disclosures of which are incorporated herein by reference. Incertain embodiments of the present invention, the molar amount ofdicarboxylic acid used in the polyphthalamide is from about 50% to about75% terephthalic acid, from about 0° A) to about 45% adipic acid, andfrom about 0% to about 35% isophthalic acid.

In certain embodiments of the instant invention, the dicarboxylic acidcomponent of the polyphthalamide comprises from about 55 mole % to about75 mole % terephthalic acid and from 25 mole % adipic acid to about 45mole %, and the diamine component comprises about 100 mole %hexamethylene diamine. In a certain embodiment of the instant invention,the dicarboxylic acid component of the polyphthalamide comprises about65 mole % terephthalic acid and 35 mole % adipic acid, and the diaminecomponent comprises about 100% hexamethylene diamine.

In certain embodiments of the present invention, the dicarboxylic acidused in forming the polyphthalamide comprises a mole ratio of aromaticdicarboxylic acid groups in the range from at least about 50 mole %aromatic groups to about 100% aromatic groups. In certain embodiments ofthe present invention, the polyphthalamide polymer comprises from about50 mole % to about 95 mole % hexamethylene terephthalamide units, fromabout 25 mole % to about 0 mole % hexamethylene isophthalamide units,and from about 50 mole %) to about 5 mole % hexamethylene adipamideunits. Suitable polyphthalamides for use in the present invention areavailable as AMODEL® polyphthalamides from Solvay Advanced Polymers,L.L.C.

Other at least partially aromatic polyamides suitable for use in thepresent invention include polyamides formed from the reaction of analiphatic dicarboxylic with an aromatic diamine. Suitable partiallyaromatic polyamides formed from aromatic diamine include the reactionproduct of adipic acid and m-xylene diamine. Such partially aromaticpolyamides are available as IXEF® polyarylamide from Solvay AdvancedPolymer, L.L.C.

Partially aromatic polyamides suitable for use in the polymercompositions according to the present invention include polyamidesformed from dicarboxylic acids and diamines, wherein up to 100 mole % ofthe dicarboxylic acids are aromatic dicarboxylic acids and up to 100mole % of the diamines are aromatic diamines.

Other aromatic polycondensation polymers suitable for use in the polymercompositions according to the present invention includepolyarylethersulfones. The polyarylethersulfone polymers used in thisinvention are defined as polyarylene compounds in which arylene unitsexist irregularly or regularly together with ether and sulfone linkages.Examples of sulfone polymers within the scope of the present inventionpolymers comprise the following structural formulae (1) to (16) where nis an integer of at least 10. Generally, the average number of repeatunits n is greater than 30 and more typically greater than about 40 toensure sufficiently high molecular weight for robust physical andmechanical integrity of the polymers when fabricated into structuralcomponents.

In certain embodiments of the present invention, the aromaticpolycondensation polymer may preferably comprise polysulfone,polyphenylsulfone, polyethersulfone, polyetherethersulfone, and blendsand copolymers thereof. The structural repeat units ofpolyphenylsulfone, polysulfone, polyethersulfone, andpolyetherethersulfone are listed below:

Preparation of polyarylethersulfones is described in U.S. Pat. Nos.4,108,837; 4,175,175; and Canadian Patent No. 847,963 which areincorporated herein by reference in their entireties. Polysulfone iscommercially available as UDEL® polysulfone from Solvay AdvancedPolymers, L.L.C. Polyethersulfone and polyphenylsulfone are commerciallyavailable as RADEL® A and RADEL® R, respectively, from Solvay AdvancedPolymers, L.L.C.

Other aromatic polycondensation polymers included in the polymercompositions within the scope of this invention include:polyamideimides, liquid crystalline polymers, polyimides,polyetherimides, polyaryletherketones, and polyphenylene sulfides. Anexample of a polyaryletherketone included within the scope of thisinvention is polyetheretherketone (PEEK). PEEK comprises polymers formedthe following structural unit:

PEEK is commercially available as VICTREX® from Victrex, LTD. ULTEM®polyetherimide is commercially available from General Electric. Liquidcrystalline polymers and polyamideimide are available from SolvayAdvanced Polymers, LLC, as XYDAR® and TORLON®, respectively.

In certain embodiments of the present invention, the polycondensationpolymer has a HDT of above 100° C. under a load of 1.82 MPa whenmeasured according to ASTM D648. In certain other embodiments of thepresent invention, the polycondensation polymer has a HDT of above 110°C. under a load of 1.82 MPa when measured according to ASTM D648. Incertain other embodiments of the present invention, the polycondensationpolymer has a heat deflection temperature HDT of below 250° C. under aload of 1.82 MPa when measured according to ASTM D648. In certain otherembodiments of the present invention, the polycondensation polymer has aheat deflection temperature HDT of below 200° C. under a load of 1.82MPa when measured according to ASTM D648. In certain other embodimentsof the present invention, the polycondensation polymer has a heatdeflection temperature HDT of below 170° C. under a load of 1.82 MPawhen measured according to ASTM D648. In certain other embodiments ofthe present invention, the polycondensation polymer has a heatdeflection temperature HDT of below 155° C. under a load of 1.82 MPawhen measured according to ASTM D648.

Polymers usually having an HDT of at most 80° C. under a load of 1.82MPa when measured according to ASTM D648, include polyamide 6, polyamide66, polyamide 12, polyethylene terephthalate, and polybutyleneterephthalate.

In certain embodiments of the present invention, the amount of polymerhaving an HDT of at most 80° C. under a load of 1.82 MPa when measuredaccording to ASTM D648 in the polymer composition is at most 2.5 weight%, based on the total weight of the polymer composition. In certainother embodiments of the present invention, the polymer composition issubstantially free of polymer having an HDT of at most 80° C. under aload of 1.82 MPa when measured according to ASTM D648.

In certain embodiments of the present invention, the polymer compositionis free of polycarbonate.

Suitable white pigments for certain embodiments of the present inventioninclude titanium dioxide, zinc sulfide, zinc oxide, barium sulfate, andpotassium titanate, and mixtures thereof. In certain embodiments of thepresent invention, the white pigment is present in the polymercomposition in a concentration of at least about 12 weight %. In certainother embodiments of the present invention, the white pigment is presentin a concentration of from at least about 4 weight %. In certain otherembodiments of the present invention, the white pigment is present in aconcentration of up to about 30 weight %. In certain other embodimentsof the present invention, the white pigment is present in aconcentration of up to about 25 weight %. The concentration of whitepigment is based on the total weight of the polymer composition. Incertain embodiments of the present invention, the white pigment istitanium dioxide.

A suitable zinc oxide is KADOX® 911, available from Zinc Corporation ofAmerica. Suitable titanium dioxide for the present invention includerutile titania, such as Kronos 2230.

In certain embodiments of the present invention, the black pigment ispresent in the polymer composition in a concentration of at least about0.0001 weight %. In certain other embodiments of the present invention,the black pigment is present in a concentration of at least about 0.0005weight %. In certain other embodiments of the present invention, theblack pigment is present in a concentration of at least about 0.0008weight %. In certain other embodiments of the present invention, theblack pigment is present in a concentration of up to about 0.02 weight%. In certain other embodiments of the present invention, the blackpigment is present in a concentration of up to about 0.01 weight %. Incertain other embodiments of the present invention, the black pigment ispresent in a concentration of up to 0.005 weight %. In certain otherembodiments of the present invention, the black pigment is present in aconcentration of up to 0.002 weight %. In certain other embodiments ofthe present invention, a black pigment concentration of about 0.0012weight % is well suited. In certain other embodiments of the presentinvention, a concentration of about 0.0016 weight % black pigment iswell suited.

Carbon blacks are suitable black pigments for certain embodiments of thepresent invention. Suitable carbon blacks include lamp blacks, furnaceblacks, channel blacks, oil blacks, and acetylene blacks. Suitablecarbon blacks for the present invention include RAVEN® carbon black,available from Columbian Chemicals Company; SHAWINIGAN BLACK®, availablefrom Chevron Phillips Chemical Company; BLACK PEARLS®, MONARCH®, andREGAL® carbon blacks, all available from Cabot Corporation, and MPCChannel Black.

Certain embodiments of the present invention, further comprise fromabout 5 weight % glass fiber. Certain other embodiments of the instantinvention further comprise up to about 25 weight % glass fiber. Certainembodiments of the present invention comprise from about 0.1 weight %antioxidant. Certain other embodiments of the present invention compriseup to about 2 weight % antioxidant. The weight percents are based on thetotal weight of the polymer composition.

Glass fibers are commercially available in continuous filament, chopped,and milled forms. Any of these forms of glass fiber can be used in thepractice of this invention. A suitable glass fiber for embodiments ofthis invention is CERTAINTEED® 910 fiberglass, available from VetrotexCertainTeed Corp. Another suitable glass fiber is fiberglass ⅛″ 3/16″available from Saint Gobain. Suitable antioxidants include IRGANOX®1098, available from Ciba Specialty Chemicals.

The compositions of the present invention, may optionally includereinforcing filler, additives, and like. Representative fibers which mayserve as reinforcing media include graphitic carbon fibers, amorphouscarbon fibers, synthetic polymeric fibers, aluminum fibers, aluminumsilicate fibers, oxide of metals such as aluminum fibers, titaniumfibers, magnesium fibers, wollastonite, rock wool fibers, steel fibers,tungsten fibers, silicon carbide fibers, alumina fibers, boron fibers,etc. Representative filler and other materials include glass, calciumsilicate, silica, clays, such as kaolin, chalk, mica, talc, and othermineral fillers and other additives such as, wollastonite, graphite,alumina trihydrate, sodium aluminum carbonate, barium ferrite, etc.Suitable polymeric fibers include fibers formed from engineeringpolymers such as, for example, poly(benzothiazole), poly(benzimidazole),polyarylates, poly(benzoxazole), polyaryl ethers, aromatic polyamidefibers such as the fibers sold by the DuPont Company under the tradename KEVLAR®, and the like, and may include mixtures comprising two ormore such fibers. The compositions of this invention may further includeadditional additives commonly employed in the art, such as thermalstabilizers, ultraviolet light stabilizers, oxidative stabilizers,plasticizers, lubricants, and mold release agents. Certain polymercompositions according to the present invention further comprise anexternal lubricant, such as PTFE or low density polyethylene (LDPE), tofacilitate extrusion. Suitable powdered PTFE for certain embodiments ofthe present invention include POLYMIST® F5A available from SolvaySolexis. The levels of such additives will be determined for theparticular use envisioned, with up to about 50 weight %, based on totalcomposition, of such additional additives considered to be within therange of ordinary practice in the polymer compounding art.

A certain embodiment of the instant invention comprises 59.5 weight %polyphthalamide, 25 weight % titanium dioxide, 15 weight % fiberglass,0.5 weight % antioxidant, and 0.0016 weight % carbon black.

Additional embodiments of the present invention include shaped articlesmade from any of the polymer compositions described herein. Thecomposition of the present invention can be molded, such as by meltfabricating, injection molding, extruding, and blow molding, to form avariety of shaped articles. Articles within the scope of this inventioninclude LED components such as reflector cups for surface mount LEDs,scramblers (covers) for seven-segment LEDs, and reflectors for any typeof LED. Such reflectors, reflector cups, and scramblers feature improvedanti-yellowing properties during heat aging, and have excellent opacityand reflectivity properties. A reflector cup 1 according to the presentinvention is illustrated in FIG. 1, with an LED element 2 positionedinside the cup 1. The shape of reflector cup 1, can be varied tooptimize light reflection. Other common shapes of reflector cups includeparabaloidal, conical, and hemispherical. A seven segment scrambler 3for an LED according to the present invention is illustrated in FIG. 2.

An additional embodiment of the present invention is the use of a blackpigment to improve the heat stability of a white-pigmentedpolycondensation polymer composition. The polymer composition comprisesat least 20 weight % of at least one polycondensation polymer having aheat deflection temperature of above 80° C. under a load of 1.82 MPawhen measured according to ASTM D648, and from 0 to 5 weight % of atleast one polymer having a heat deflection temperature of at most 80° C.under a load of 1.82 MPa when measured according to ASTM D648.

Another additional embodiment of the present invention is a polymercomposition comprising at least 20 weight % of at least onepolycondensation polymer having a heat deflection temperature of above80° C. under a load of 1.82 MPa when measured according to ASTM D648.The composition further comprises from 0 to 5 weight % of at least onepolymer having a heat deflection temperature of at most 80° C. under aload of 1.82 MPa when measured according to ASTM D648, and a whitepigment. After 3 hours of heat aging at 170° C. the polymer compositionhas a reflectivity of greater than 65% at a wavelength of 420 nm.

The invention will be further described by examples. The examples areillustrative of the present invention and do not limit the scope of theclaimed invention.

EXAMPLES Example 1

44.625 pounds of an AMODEL® polyphthalamide comprising, as thedicarboxylic acid component, about 65 mole % terephthalic acid and 35mole % adipic acid, and, as the diamine component, about 100 mole %hexamethylene diamine, having a HDT measured according to ASTM D648under a load of 1.82 MPa of 120° C., was blended with 11.25 pounds ofSaint Gobain fiberglass ⅛″ 3/16″, 18.75 pounds Kronos® 2230 titaniumdioxide, 0.0012 pounds MPC channel black, and 0.375 pounds of IRGANOX®1098 to form a polyphthalamide composition with excellentanti-yellowing, opacity, and reflectivity properties.

The properties of the polymer composition of Example 1 are listed inTable 2.

TABLE 2 Example 1 Properties TEST VALUES Tensile Strength (psi) 13,850Tensile Elongation (%) 1.2 Tensile Modulus (kpsi) 1260 Flex Strength(psi) 24,820 Flex Strain (%) 2.39 Flex Modulus (kpsi) 1094 Notched Izod(ft-lb/in) 0.46 HDT @ 1.82 MPa (264 psi) (° C.) 290.6 Ash (%) 40.24Pellet IV (dl/gr) 0.98 Moisture (ppm) 570 Pellet Density (kg/m³) 1.56

Table 3 lists the carbon black content of Control C1 and Examples 2, 3,and 4. MPC Channel Black was used in each of the Examples. The carbonblack was added to 75 pounds of polyphthalamide composition. Thecompositions C, 2, 3, and 4 are substantially similar to Example 1,except the amount of carbon black in each composition is different fromeach other, as shown in Table 3.

TABLE 3 Carbon black content of polyphthalamide compositions. ExamplesC1 2 3 4 Carbon Black 0 0.0012 0.0009 0.0016 Content (%)

The reflectivity data of the molded compositions according to theinstant invention before and after heat aging are listed in Tables 4 and5, and plotted in FIGS. 3 and 4. Heat aging is performed for three hoursat 170° C. in a forced air oven at ambient humidity. Reflectivity ofplaques formed from the polymer compositions is measured using acolorimeter. Light from a xenon arc source impinge on the plaques at anoblique angle and light reflected from the surface of the plaque iscollected by the colorimeter through an adjustable wavelength filter.Thus, reflectivity is measured at a number of different wavelengths. Thereflectance of the plaques is compared to the reflectance of a knownstandard. The decreased reflectivity of the compositions afterheat-aging is a result of the yellowing of the composition. As shown inFIG. 4, after heat aging, the compositions of the present invention,have improved reflectivity in the shorter visible wavelengths (blue endof visible spectrum), hence there is less yellowing than the controlcomposition.

TABLE 4 Reflectivity Before Heat Aging Reflectivity (%) WavelengthExamples (nm) C1 2 3 4 400 46 45 45 45 420 81 82 84 84 440 86 85 88 87460 87 85 88 87 480 88 85 88 87 500 89 86 88 87 520 90 86 88 87 540 9086 89 87 560 90 86 88 87 580 90 85 88 87 600 90 85 88 87 620 90 85 88 87640 90 85 88 87 660 90 85 88 86 680 90 85 88 86 700 90 85 88 86

TABLE 5 Heat Aged Reflectivity Reflectivity (%) Wavelength Examples (nm)C1 2 3 4 400 41 43 43 44 420 62 70 70 71 440 67 73 74 75 460 70 76 76 77480 73 77 78 79 500 76 79 80 81 520 79 80 82 82 540 81 81 83 83 560 8483 85 84 580 85 83 85 85 600 86 83 86 85 620 87 84 86 85 640 88 84 87 86660 89 84 87 86 680 89 84 87 86 700 89 84 87 86

The embodiments illustrated in the instant disclosure are forillustrative purposes. They should not be construed to limit the scopeof the claims. As is clear to one of ordinary skill in this art, theinstant disclosure encompasses a wide variety of embodiments notspecifically illustrated herein.

1. A polymer composition comprising: at least 20 weight %, based on thetotal weight of the polymer composition, of at least onepolycondensation polymer having a heat deflection temperature of above80° C. under a load of 1.82 MPa when measured according to ASTM D648;from 0 to 5 weight %, based on the total weight of the polymercomposition, of at least one polymer having a heat deflectiontemperature of at most 80° C. under a load of 1.82 MPa when measuredaccording to ASTM D648; a white pigment a black pigment present in aconcentration of up to 0.005 weight %, based on the total weight of thecomposition,
 2. The polymer composition according to claim 1 wherein thepolycondensation polymer is selected from the group consisting of atleast partially aromatic polyamides, polyamideimides, liquid crystallinepolymers, polyimides, polyetherimides, polyaryletherketones,polyarylethersulfones, polyphenylene sulfides and polycarbonates.
 3. Thepolymer composition according to claim 2 wherein the polycondensationpolymer is a polycarbonate.
 4. The polymer composition according toclaim 2, wherein the polycondensation polymer is an at least partiallyaromatic polyamide.
 5. The polymer composition according to claim 4,wherein the at least partially aromatic polyamide is a polyphthalamideformed from terephthalic acid and an aliphatic diamine, and optionally,in addition, isophthalic acid and/or an aliphatic dicarboxylic acid. 6.The polymer composition according to claim 2, wherein thepolycondensation polymer is a polyarylethersulfone.
 7. The polymercomposition according to claim 6, wherein the polyarylethersulfone isselected from a polysulfone, a polyphenylsulfone and a polyethersulfone.8. The polymer composition according to claim 1 wherein said at leastone polymer having a heat deflection temperature of at most 80° C. undera load of 1.82 MPa when measured according to ASTM D648 is present from0 to 2.5 weight %, based on the total weight of the polymer composition.9. The polymer composition according to claim 1 wherein said whitepigment is present in a concentration of at least 4 weight %, based onthe total weight of the composition.
 10. The polymer compositionaccording to claim 9, wherein the white pigment is present in aconcentration of at least 12 weight %, based on the total weight of thecomposition.
 11. The polymer composition according to claim 1 whereinsaid black pigment is present in a concentration of at least 0.0001weight %, based on the total weight of the composition.
 12. The polymercomposition according to claim 1, wherein the white pigment is titaniumdioxide.
 13. The polymer composition according to claim 1, wherein theblack pigment is a carbon black.
 14. The polymer composition accordingto claim 1, wherein the polycondensation polymer is present in aconcentration of at least 40 weight %, based on the total weight of thecomposition.
 15. Shaped article formed from the composition according toclaim
 1. 16. The shaped article according to claim 15, wherein it isselected from the group consisting of a reflector for an LED, areflector cup for a surface mount LED, and a scrambler for aseven-segment LED.